Since the eighties and nineties of twentieth century, forgery and counterfeiting crime have become another global public hazard besides traffic in drugs, smuggling and environmental pollution day by day. According to statistics of authorities, the total output
The retroreflective layer is an optical material having high refractive index, preferably glass or PC (polycarbonate) and etc.;
The material of the photopolymerizable information layer comprises components having the following weight percentages:
photopolymerization monomer: 20%-60%
photoinitiator: 1%-10%
binder: 30%-79%
with the sum of the percentages of the above respective component being 100%.
Preferably, the material of the photopolymerizable information layer comprises components having the following weight percentages:
photopolymerization monomer: 25%-50%
photoinitiator: 2%-8%
binder: 42%-73%
The photopolymerization monomer is one or more selected from the group consisting of EM210 (2-phenoxyethyl acrylate), EM2211 (ethoxylated 1,6-hexanediol diacrylate), EM224 (polyethylene. glycol (200) diacrylate), APG-400 (alkyl polyglucoside) and BPE-500 (ethoxylated bisphenol A dimethacrylate).
The binder is one or more selected from the group consisting of acrylic acid, methacrylic acid, methyl methacrylate and 2-ethylhexyl acrylate;
The photoinitiator is one or more selected from the group consisting of benzophenone, diethylamino benzophenone, leuco crystal violet and toluenesulfonic acid monohydrate;
The reflective layer is the material having high reflectance, preferably Al (aluminum), Ag (argentum) or Cr (chromium);
The process for preparation of the anti-counterfeiting film comprises the following steps:
(1) coating the binder layer material over the protective layer; embedding the retroreflective layer material into the binder layer and drying at 100° C.-130° C. for 2-3 minutes; coating the photopolymerizable information layer over the retroreflective layer and drying at 100° C.-150° C. for 3-5 minutes to obtain a retroreflective film;
(2) placing the upper surface of the protective layer 1 of the above retroreflective film beneath an exposure template configured with template graphics; subjecting the retroreflective film to first exposure treatment via the linear polarized ultraviolet, an exposure time being 0.1-0.9 seconds, an exposure energy being 30-50 mJ/cm2, an exposure angle being 60-90°;
By radiation with ultraviolet light, photopolymerization monomer molecule is subjected to polymerization reaction along the polarization direction of the ultraviolet light. By virtue of special optical structure of directional retroreflective film, the photopolymerization monomer is subjected to polymerization reaction only along the direction consistent with the polarization direction of the ultraviolet light so as to change the optical property thereof and form the graphics information consistent with the exposure template;
Changing the graphics of the exposure template and the exposure angle, subjecting the retroreflective film to second exposure treatment via linear polarized ultraviolet light, the exposure time being 0.1-0.9 seconds, the exposure energy being 30-50 mJ/cm2, the exposure angle being 15-60°; so as to form different graphics information at another angle; then high-vacuum vapor-depositing a reflective layer material on the photopolymerizable information layer to obtain the anti-counterfeiting film of the present invention;
The term “exposure angle” means the angle between the exposure light source and the anti-counterfeiting film;
Preferably, angle difference between the first exposure treatment and the second exposure treatment is 30-50°;
Further, during the preparation process of the above anti-counterfeiting film, the exposure template is lighttight polyester material, metal material or lighttight glass and etc.;
The exposure template may also be various transmissive displays such as TN-LCD (twisted nematic liquid crystal display), ECB-LCD (electrically controlled birefringence liquid crystal display), PC-LCD (phase change liquid crystal display), STN-LCD (super twisted nematic liquid crystal display) or TFT-LCD (thin film transistor liquid crystal display) and etc.; by changing the display information Thereon, different types of graphics information such as randomly changed number can be prepared on the above retroreflective film; said randomly changed number has been widely used for logistics management and anti-counterfeiting of information.
The anti-counterfeiting film of the present invention has an effect that visible graphics information can change along with the visual angle. The effect that the visible graphics information can change along with the visual angle of the present invention means that graphics A can be seen when viewing at a special angle a, after transforming the viewing angle into b, the graphics A disappears or graphics B can be seen, transformation of multiple graphics information between multiple angles can be achieved according to different techniques.
The anti-counterfeiting film of the present invention has special anti-counterfeiting effect and thus is liable to be identified, its special visual effect prominently differs from anti-counterfeiting technologies such as laser holography, visual angle color and precision printing; furthermore, such technique can be identified by naked eyes without any tools and is liable to be identified by consumers. The present invention introduces the directional retroreflective technique into the anti-counterfeiting field to impart special anti-counterfeiting characteristics to it so as to improve technological barriers and enlarge anti-counterfeiting capability grade.